1. Technical Field
The disclosure relates to an image processing device, an imaging device, a microscope system, an image processing method, and a computer-readable recording medium for performing image processing on an image acquired by imaging a specimen or the like.
2. Related Art
In recent years, a so-called virtual slide technology has been known that records an image acquired by imaging a specimen placed on a slide glass as electronic data and allows a user to observe the image on a monitor of a personal computer or the like. According to the virtual slide technology, by sequentially stitching partial images of a specimen enlarged by a microscope, a high-resolution image on which the whole specimen is shown is built. In other words, the virtual slide technology is a technology for generating an image of which the visual field for a subject is enlarged by acquiring a plurality of images of the same subject having different visual fields and stitching the images.
A microscope includes a light source for illuminating a specimen and an optical system for enlarging an image of the specimen. In a later stage of the optical system, an image sensor for converting an image of an enlarged specimen into electronic data is provided. For this reason, brightness unevenness may occur in an acquired image due to illumination unevenness of a light source, non-uniformity of an optical system, irregular characteristics of an image sensor, and the like. This brightness unevenness is called shading, and, generally, a part of an image is darker as the part is located farther from the center of the image corresponding to the position of an optical axis of the optical system. For this reason, in a case where a virtual slide image is generated by stitching a plurality of images, an unnatural boundary is generated in a portion stitching the images. Since the shading is repeated by stitching the plurality of images, the virtual slide image is seen as if a periodical pattern is present in the specimen.
In order to address such a situation, a shading correction technology has been known that acquires a shading pattern as a calibration image in advance and corrects an image in which a specimen is shown based on the calibration image. For example, JP 2006-171213 A discloses a shading correction technique in which imaging is performed when a specimen is retracted outside of the angle of view of the optical system at the time of a transmitting illumination observation, and an image acquired by performing imaging when a reflection member is arranged within the angle of view of the optical system, is used as a calibration image at the time of epi-illumination observation.
JP 2008-51773 A discloses a method of acquiring data used for a shading correction by performing imaging using a uniform fluorescent sample as a calibration sample at the time of a fluorescence observation.
JP 2013-257422 A discloses a technique in which a reference visual field image that is an image in a predetermined visual field range of a sample is captured, the position of the sample is relatively moved with respect to an optical system, a plurality of peripheral visual field images that include a predetermined area within the predetermined visual field range and are images of a peripheral visual field range different from the predetermined visual field range are captured, and a correction gain of each pixel of the reference visual field image is calculated based on the reference visual field image and the peripheral visual field images.